Can You Put Epsom Salt in a Hot Tub?

Soaking in a hot tub provides the ultimate relaxation experience, and it’s the reason many homeowners purchase a hot tub in the first place. The warm water and massaging jets soothe muscles and melt away stress.

Boosting this experience by adding in Epsom salt, a magnesium sulfate compound known for its therapeutic benefits, seems like a good idea, right? Epsom salt is often sprinkled into bathtubs or foot soaks because the magnesium can improve muscle function and reduce inflammation.

However, adding Epsom salt to a hot tub can actually cause problems — quite the opposite of relaxation.

Can You Put Epsom Salt in a Hot Tub?

No. It can disrupt the chemical balance, hinder sanitizer performance and cause corrosion.

“Visually, it’s unlikely you will see anything happen at all, leading you to believe that it’s OK to carry on,” says Terry Marsh, a certified hot tub technician and owner of Hyperion Hot Tubs. “However, it’s possible that you will upset the pH balance of your hot tub, something you will no doubt have spent some time perfecting.”

Epsom salt is slightly acidic. Adding it to your hot tub will disrupt the alkalinity and pH balance. “Maintaining the correct pH of your spas water is critical, not only for your own health, but also the long-term health of your spa’s components,” says Marsh.

An improper chemical balance can hinder the performance of the tub’s sanitizer, whether chlorine or bromine. That allows bacteria to grow that can cause skin irritation or infections.

Also, over time, Epsom salt may corrode critical hot tub components like gaskets, seals and metal parts. It can lead to earlier-then-expected failure or malfunction of the heater or pump. “It’s also likely you could adversely impact your spa’s warranty,” Marsh says.

Whether you have an indoor or outdoor hot tub, Marsh says you should avoid using Epsom salt. “The location of the spa would not have any effect on the water chemistry.”

Alternatives to Epsom Salt

If you’re still searching for a product to support a relaxing soak in your hot tub, you have options.

“There are many products on the market that are specifically designed for use in a hot tub,” says Marsh. “They are formulated so that they will not adversely affect your spa’s water and its pH value.”

Some alternatives to Epsom salt include:

• Hot tub aromatherapy products: Many aromatherapy products specifically for hot tub are out there. Some even contain Epsom salt. However, as long as you use the recommended dosage, the product will not disrupt your water chemistry. One of the most popular, according to Marsh, is the Spazazz line of aromatherapy crystals.
• Hot tub spa salts: Look for Dead Sea mineral salts formulated for hot tub use.
• Hot tub spa elixirs: Spa elixirs also provide a relaxing hot tub experience. These soften the water and moisturize your skin without compromising the chemical balance.

Note: Although baking soda is often recommended as an alternative to Epsom salt, Marsh says to stay away. “It will increase the total alkalinity (TA) of the water,” he says, “which could throw your pH out of range and may promote the formation of scale in the hot tub.”